The present invention relates to a sample introducing interface system defined by a sample introducing apparatus and sample modules connectable therewith for direct analysis and measurement of volatile and partially volatile organics or organic compounds obtainable from various environmental matrices in mass spectrometers.
The analysis and measurement of trace levels of volatile and partially volatile organics and organic compounds in environmental matrices such as air, water, and soil has been achieved by employing direct sampling mass spectrometry. Such monitoring of environmental matrices is becoming of increasing interest due to environmental pollution concerns. In direct sampling mass spectrometry, a sample of the organic or organic compound in gaseous form is directly inserted into the high vacuum region of the mass spectrometer without first undergoing sample preparation such as provided by the use of gas chromatography or other sample separating procedures. By directly introducing a sample into the high vacuum region of the mass spectrometer, the response time for the analysis of the sample is substantially instantaneous with the analysis providing an accurate quantification of target analytes. In direct sampling mass spectrometry, the individual organics or organic compounds are analyzed by using one or more techniques such as spectra subtraction, selective chemical ionization, and tandem mass spectrometry.
Mass spectrometers useful in the practice of direct sampling mass spectrometry are presently commercially available and include ion trap mass spectrometers such as provided by Finnigan MAT Corporation, San Jose, Calif., 95134-1991. Ion trap mass spectrometers are provided with vacuum chambers which are pumped to high vacuum with one or more turbomolecular pumps. The vacuum chamber and the analyzer cell within the mass spectrometer are preferably maintained at a constant temperature of about 120.degree. C. to help minimize the absorption of contaminants on exposed surfaces in the mass spectrometer. The ion trap mass spectrometers are preferably equipped with the necessary hardware and software for performing electron impact, chemical ionization, selective ion ejection, and collision induced dissociation multiple-step mass spectrometry experiments.
Another type of mass spectrometer which can be utilized for the direct sampling of volatile organics or organic compounds is provided by a tandem source quadrupole mass spectrometer. This type of spectrometer performs electron input measurements and can include a glow discharge ionization source. Ions generated by glow discharge ionization are passed through a lens assembly into the high vacuum region of the mass spectrometer where they enter the lens assembly of the electron impact source and are subsequently focused into the mass analyzer.
The introduction of samples of volatile and partially volatile organics and organic compounds into high vacuum regions of mass spectrometers such as generally described above has been achieved by utilizing a transfer interface attached to a standard gas chromatograph or other sample preparing mechanism. The transfer interface conveys the prepared gaseous sample into the high vacuum region of the mass spectrometer by using a capillary column which, at least partially, extends between the gas chromatograph or other sample preparing mechanism to the high vacuum chamber of the mass spectrometer. The capillary column is supported in a tube assembly that is fixedly attached to the mass spectrometer and to the gas chromatograph or other sample preparing mechanism. The tube assembly is maintained under vacuum and is provided with a heating arrangement for heating the capillary to a sufficient temperature to prevent adsorption of volatiles on inner surface regions thereof. While such a transfer interface provide for the transfer of the sample to the mass spectrometer from a gas chromatograph or other sample preparing mechanism, the changing of the mass spectrometer from one type of sampling configuration to another type of sampling configuration requires that the mass spectrometer be shut down. Consequently, analyses of environmental samples contained in different matrices such as air, soil, and water have typically been conducted by using separate mass spectrometers that are individually dedicated to a particular sampling configuration such as for soil/water analysis, thermal decomposition analysis, or analysis of an air sample from a suitable source such as the atmosphere since there was no mechanism previously available for changing a single mass spectrometer from one type of sampling configuration to another type of sampling configuration without undergoing a time consuming operation requiring the shutting down of the mass spectrometer.